|PowerColor AX6950 PCS++ Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Bruce Normann|
|Tuesday, 22 February 2011|
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PowerColor PCS++ HD 6950 Detailed Features
The full PWM-based voltage regulator section that supplies power to the HD 6950 GPU is shown here. It is a 6+1 phase design that is controlled by a relatively new chip: the CHL8228 from CHiL Semiconductor Corporation. It is a dual-loop digital multi-phase buck controller specifically designed for GPU voltage regulation. Dynamic voltage control is programmable through the I2C protocol. CHil's first big design win in the graphics market was with a slightly simpler 6-phase chip in the GTX480 Fermi card, a power monster if there ever was one. The CHL8228 has 8 phases available for use, and the phases can be grouped any way the designer wants. In this case, six are used for the GPU and one of the two remaining is used to supply power to the memory. That leaves one phase unused, which is very common once you get above four phases. Designers tend not to use odd numbers, because they rarely use more than four steps to ramp the current delivery up and down as the load varies. The last phase could have been used to supply 2-phase power to the memory, but the benefit would likely be mostly psychological.
The CHL8228 is fully compatible with the I2C communication protocol, which makes software controlled voltage adjustments a walk in the park. PWM controllers without this capability require more work from the BIOS designer to provide voltage control, and the methods are almost always specific to one or two cards, and cannot be accessed by the most common monitoring and control utilities, such as MSI Afterburner.
The VRM section also features another relatively new chip in this application space; a DrMOS design from Texas Instruments that includes both the driver transistors and the High-Low MOSFET pair in one tightly integrated package. They are positioned right above the R19 chokes in the image above. It's a very small device, with markings of 59901M, and it's so new I can't find any specs for it. It has a bit of a reputation already though, as it was initially being blamed for the production delays of the AMD 6900 series cards. Apparently, it was in short supply for some unexpected reason, so AMD and their AIB partners had to do a fast workaround to get the first Radeon HD6970 and HD6950 cards to market. It saves a huge amount of board space, and a full complement of discrete MOSFETs and drivers for low side and high side circuits would not have fit so easily in this area of the board.
This new DrMOS chip is considerably smaller than previous parts. It's only 6mm x 5mm, where many of the recent DrMOS designs were 8mm x 8mm. It doesn't sound like such a big change, but the new part has less than half the surface area (30mm2 v. 64mm2). There is a single copper heatsink for the DrMOS chips, that's a custom design for this card. Unfortunately the design allows the board assembly technicians to place it on the board in either orientation, and if they get it wrong, it looks OK but doesn't contact the IC package nearly as well. I had to flip mine around to get it placed correctly. The Japanese quality mavens have a quality management technique they call poka-yoke that could have been used to prevent this. The part design should only allow it to fit in one orientation, thereby mistake-proofing the assembly.
It's hard to believe, but this little switch is what this video card is all about. While this isn't the first card to utilize a dual BIOS arrangement, it is the first one to offer a "free" upgrade to the next level of GPU specification, right out of the box. I know several of our readers are proficient at flashing the BIOS of their graphics card, and I've done it a couple of times for a variety of reasons, but it's still not a frequent thing for most enthusiasts to do. In my years of reading various forums, it's also the single most common cause that I see of the condition known as bricking, as in "I bricked my video card...!" Oddly enough, the last big occurrence of a BIOS Flash Mob was when the ATI HD 4830 cards were widely tapped to receive an instant upgrade to HD 4850 status. Even though the success rate was well over 50%, a large number of people learned the hard way that nothing in life is guaranteed. Now for the very first time, PowerColor is offering the general user that guaranteed boost. Through testing, binning, or some other selection method, they are offering an HD 6950 GPU that WILL unlock to HD6970 specs with the flip of a switch.
The PC board had some of the best solder quality and precision component placement that I've seen recently, as you can also see above. This is the area on the back side of the board, directly below the GPU, and it's one of the most crowded sections of any graphics card. On my LCD screen, this image is magnified 20X, compared to what the naked eye sees. The smallest SMD capacitors located in this view are placed on 1mm centers.
This board was also well above average for cleanliness, compared to some of the samples I've looked at recently. There were some traces of residue across different sections of the board, but they were minor. All manufacturers are under intense pressure to minimize the environmental impact of their operations, and cleaning processes have historically produced some of the most prolific and toxic industrial waste streams. The combination of eco-friendly solvents, lead-free solder, and smaller SMD components have made cleaning of electronic assemblies much more difficult than it used to be.
The memory choice for the PowerColor PCS+ HD 6870 2GB GDDR5 is consistent with the AMD reference design for the HD 6950. The basic Radeon HD 6950 specs require 1250 MHz chips for the memory, which is exactly what these Hynix H5GQ2H24MFR-T2C GDDR5 parts are designed for. They need 1.5V to do it; at 1.35V they are only good for 900 MHz. The stock Radeon HD 6970 cards have a 1375 MHz memory clock, and require the "-ROC" version of this chip to run at that speed. The lower spec memory chips on this graphics card are the only thing keeping it from running at identical settings as the HD 6970. Because there's 2 GB of RAM, the cost for the upgrade would probably be substantial, and PowerColor is trying to keep the cost low for this board, so 1250 MHz it is.
Before we move into the testing phase of the review, let's take a detailed look at the features and specifications for the new AMD Radeon HD 6950 GPU. AMD and PowerColor have supplied us with a ton of information, so let's go....